1. Field of the Invention
The present invention relates to a scroll type compressor and particularly relates to a scroll type compressor suitable for being non-exclusively incorporated in a refrigerating system of a vehicle to be driven by a vehicle engine.
2. Description of the Related Art
Generally, a conventional scroll type compressor includes a housing to which a stationary scroll element is attached so that a movable scroll element, accommodated in the housing, implements orbiting motion with respect to the stationary scroll element. The stationary scroll element includes a stationary end plate and a stationary spiral member, and the movable scroll element includes a movable end plate and a movable spiral member. The stationary and movable scroll elements are engaged with one another to form compression chambers therebetween, and the compression chambers are shifted from an outer end of the stationary scroll member toward a center thereof so as to reduce the respective volumes thereof during the orbiting motion of the movable scroll element with respect to the stationary scroll element. Thus, a fluid to be compressed, such as refrigerant gas, is compressed in the volume-reduced compression chambers. The refrigerant gas delivered from the scroll type compressor is circulated through the refrigerating system to return to the compressor.
In the conventional scroll type compressor as disclosed in Japanese Unexamined Patent Publication (Kokai) No. 3-100389, the stationary scroll element is housed in a casing forming a part of the housing, and front and rear housings are attached to front and rear ends of the casing, respectively. Namely, the stationary scroll element is formed as an element separate from the casing, and has a stationary spiral element formed as a spirally extending projection projecting from an end face of a stationary end plate. Therefore, a gap necessarily appears between the stationary spiral element and the casing to form a suction chamber having a large volume. The compressor is further provided with a suction port formed in the casing and arranged to communicate with the suction chamber. Thus, the refrigerant gas returning from the refrigerating system is introduced into the suction chamber via the suction port, and a large part of the refrigerant gas is sucked into the compression chambers to be compressed therein while the respective compression chambers are shifted. However, some part of the refrigerant gas is conducted into the front housing to cool and lubricate a bearing device rotatably supporting the movable scroll element and a self-rotation preventing unit for preventing a movable scroll element from implementing a self-rotation during its orbiting motion which are housed in the front housing. A further part of the refrigerant gas is conducted to a slidably engaging portion of the movable and stationary elements to cool and lubricate the engaging portion. The lubrication is achieved by a lubricating oil mist mixed with the refrigerant gas. The refrigerant gas after cooling and lubricating the above-mentioned device, unit and portion is eventually sucked into the compression chambers to be compressed therein.
Japanese Unexamined Patent Publication (Kokai) No. 7-133768 discloses a scroll type compressor of the type wherein a stationary scroll element has a shell portion thereof forming a part of an outer shell of the compressor. Thus, the shell portion is provided with a stationary end plate and a stationary spiral member which is obtained by forming a spiral groove in the shell portion. The scroll type compressor of JP-A-7133768 has a front housing attached to a front end of the shell portion, and the front housing is provided with a suction port formed therein to introduce refrigerant gas into the interior of the front housing. Therefore, the refrigerant gas in the interior of the front housing may be used for cooling and lubricating a bearing device for rotatably supporting a movable scroll element before it is sucked into compression chambers formed between the movable and stationary scroll elements to be compressed therein.
Nevertheless, in the above-described conventional scroll type compressors of JP-A-3100389 and JP-A-7133768, the suction chamber permits the refrigerant gas to be expanded therein, and the bearing device, the self-rotation preventing unit and other portions cooled and lubricated by the refrigerant apply heat to the refrigerant gas before the refrigerant gas is sucked into the compression chambers. Therefore, the scroll type compressors cause a pressure loss of the refrigerant gas due to the expansion thereof, and accordingly, produce an increase in the specific volume of the refrigerant gas before the gas is sucked into the compression chambers. Thus, the conventional scroll type compressors cannot meet a recent requirement for an enhancement of the compression performance.
If the refrigerant gas containing therein lubricating oil mist for lubricating the bearing device and other movable portions of the compressor is directly compressed and delivered into the refrigerating system, a defect occurs in which the refrigerating performance of the refrigerating system must be lowered due to existence of the oil component in the refrigerant. Thus, in order to overcome such defect, Japanese Unexamined Patent Publication (Kokai) No. 3-129273 discloses a scroll type compressor of the type wherein an oil-separating chamber for separating a lubricating oil component from the refrigerant gas after being compressed, and a oil-storing chamber for storing the separated oil therein are arranged in the housing. The oil-storing chamber is arranged to receive the oil separated from the refrigerant gas in the oil-separating chamber. The oil-storing chamber fluidly communicates with movable portions of the compressor such as a bearing device for rotatably supporting a movable scroll element, a self-rotation preventing unit for preventing the movable scroll element from implementing a self-rotation during its orbiting motion, and an engaging portion of the stationary and movable scroll elements via oil-supply passages. Thus, lubricating oil can be supplied for lubricating the bearing device, the self-rotation preventing unit, and the engaging portion of stationary and movable scroll elements. Further, since refrigerating gas from which the oil component is separated is delivered to the refrigerating system, the afore-mentioned defective reduction in the refrigerating performance of the refrigerating system does not occur.
Nevertheless, the oil-supply passage which provides a fluid communication between the oil-storing chamber and the engaging portion of stationary and movable scroll elements must usually be very small, and accordingly, the oil-supply passage might be plugged by metallic powder, produced by abrasion of the stationary and movable scroll elements, having a smallest diameter of at most 50 micro-meters. The abraded metallic powder adheres to a portion around an entrance of the oil-supply passage which opens toward the stationary spiral member of the stationary scroll element, and prevents the lubricating oil from being supplied to the engaging portion of the movable and stationary scroll elements or reduces the amount of the lubricating oil supplied to the engaging portion. Accordingly, a lack of lubrication occurs in the engaging portion of the movable and stationary scroll elements. Further, the metallic abrasion powder adhering to the portion around the entrance of the oil-supply passage might prevent the movable scroll element from implementing a smooth orbiting motion thereof, and accordingly, a reliable operation of the scroll type compressor cannot be ensured. Particularly, when the operation of the scroll type compressor is started after a long stopped condition at a high temperature, the liquid-phase refrigerant is initially sucked into the compression chambers so as to cause liquid compression. As a result, the movable scroll element collides against the stationary scroll element during the orbiting motion of the movable scroll element, and accordingly, production of the abraded metallic powder is unfavorably increased to easily cause the above-mentioned problem.